The goal of this research program is to better understand the effects, and limitations, of cognitive factors in human autonomic classical conditioning. The autonomic measures include a variety of components of the skin conductance response and the heart rate response. The proposed experiments are concerned with three major issues: (1) Do cognitive/autonomic dissociations occur with "biologically prepared" CS-UCS contingencies and not with "biologically unprepared" contingencies? Dissociations will be tested with both types of contingencies while examining long-term retention of autonomic CRs and conditioned inhibition. (2) Can previously established autonomic CRs be performed without the subjects' awareness of the CSs' presence? Unaware performance will be tested within a dichotic listening paradigm with special emphasis on possible cerebral laterality effects. (3) Are moment-by-moment changes in cognitive processing demands during the conditioning session related to the degree and topography of autonomic CRs? Cognitive processing demands will be monitored by measuring subjects' performance on a continuous secondary task during conditioning. Conditioning variables will be manipulated while the degree and time course of both cognitive processing demands and autonomic CRs will be measured.